The present invention relates generally to a pressure applying device and more specifically relates to a device for measuring the amount of compressive force that is applied to elastomeric material, such as gaskets.
With the advent of filter press membrane electrolytic cells for the production of chlorine in alkali metal hydroxides, there has been increased attention given to efficient manufacture and assembly of components that comprise chlor-alkali cells. The development of separators that have ion-exchange properties, such as the membranes marketed by E. I. DuPont de Nemours & Co. under the trademark Nafion.RTM. and by Asahi Glass Company under the trademark Flemion.RTM., have heightened the interest in the filter press type of cell. These cells are generally assembled so that they stand vertically and have alternately positioned cathodes and anodes, separated by the membranes, which are compressed together in a fluid-tight arrangement by hydraulic stud tensioners or other mechanical compression assembly apparatus.
In order to effect this fluid-tight sealing, means, such as elastomeric gaskets, have been employed between each electrode and the intervening membrane in an attempt to both effect the fluid-tight seal and to prevent damage to the membrane. One of the problems encountered with this type of assembly lies in the proper selection of gaskets which deform uniformly without excessive pressure to effect the fluid-tight seal. The need to effect compression without excessive pressure is important to prevent potential damage from occuring to the membrane separators between the electrodes, as well as to ensure that warping or failure of the electrode frames themselves does not occur.
Since the gaskets employed in the assembly of filter press cells are obtained from a number of suppliers, there is frequently substantial difference between one manufacturer's product and another's product, as well as a difference between the products supplied from the same manufacturer. The difference in the quality of the gaskets of allegedly the same durometer normally was not discovered until the cell was assembled and filled with electrolyte fluid. Thus, when a problem was discovered, the cell had been placed in an operating condition and the electrolyte fluid was found to leak due to faulty gaskets. To correct the situation, a filter press type of cell would then have to be drained of its electrolyte fluids and disassembled. All of this, naturally, was time-consuming and wasteful of effort.
Thus, there is a need to establish whether a gasket is suitable for use within a filter press type of cell prior to actual incorporation into its assembled unit. Additionally, there is a need to check for defective gaskets and to establish the exact amount of pressure that must be effected by the exertion of compressive forces against the electrode frames in order to compress the rubber gasket material to the desired degree. It has been found that pressure within the range of 600 to 700 pounds per square inch is optimum to reduce the potential for damage to the membrane separators, as well as to compress the rubber gaskets about 30 to 35% of their original thickness. This percent compression has been found to be the optimum range of compression recommended by the gasket manufacturers to effect uniform fluid-tight sealing and optimum gasket performance. Heretofore, there has been no convenient way to pretest the gaskets to be employed in the assembly of a filter press type of cell prior to assembly.
It is to be understood that the term compression as used heretofore and as will be used hereafter includes the concept of deformation, especially when applied to use in conjunction with gaskets. The gaskets, when compressed, actually deform in response to the compressive forces, expanding or deforming in the unrestrained directions.
These problems are solved in the design of the apparatus comprising the present invention by providing a device for determining the amount of a compressive force exerted on elastomeric material, such as a gasket, and the amount of compression experienced by the tested material prior to its insertion in a filter press membrane electrolytic cell.